The present invention relates an image processing apparatus and method for constructing a functional image which image, is used for analyzing the motion of a fluid in tissue from plural images of one section of the tissue as measured by a medical apparatus, like an X-ray CT apparatus.
To dynamically analyze information about fluid moving in an object to be examined, it is necessary to continually pick up plural images of one part of the object for measuring a change in the part with the passage of time. For example, an X-ray CT apparatus continues to measure a target section of the object for several tens of seconds after a contrast medium is injected into the object. By reconstructing the measuring data as images, plural tomographic images of one and the same section of an object part can be obtained. Assuming that an apparatus designed to continuously do with-turn and one-second scans operates to measure a part of the object for thirty seconds, thirty time-serial CT images can be obtained.
As a method for analyzing the motion of a fluid in an object part to be examined based on such serial CT images, there has been proposed a method for obtaining an approximation of each pixel with a function and constructing an image of a feature amount of the approximate function. Concretely, the method takes the steps of obtaining an approximation with a gamma function and deriving a maximum value and the time needed to reach the maximum value for forming an image of the target diagnosis part. This image captures a functional feature of an object part to be examined (for example, blood flow). This image is thus referred to as a functional image.
In this method, image noise and operating time are inhibitive factors. The image noise is likely to inhibit the ability to execute a proper approximation, thereby lowering the quality of a functional image. More and higher definitive images result in expanding each image matrix and increasing the amount of data, thereby increasing the operating time.
Another problem is an exposure against an object to be examined, though it actually depends on the necessary amount of data. The improved performance of an X-ray CT apparatus makes it possible to measure a target object part plural times at short intervals for the purpose of capturing the motion of fluid. However, it is necessary to emit sufficient radioactive rays for achieving a sufficient image quality at each measuring time. Hence, the amount of radioactive rays is increased with an increase of the measuring time.